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article imageWorld-Renowned Arecibo Radio Telescope can't be saved

By Karen Graham     Nov 20, 2020 in Science
The world-renowned radio telescope at the Arecibo Observatory in northern Puerto Rico, now on the brink of collapse, is set to be withdrawn from service, the National Science Foundation (NSF) announced today.
The iconic telescope was completed in 1963, and up until 2016, the Arecibo Observatory's 1,000 foot (305 meters) radio telescope was the world's largest single-aperture telescope. William E. Gordon of Cornell University oversaw its design and intended to use it to study the Earth's ionosphere.
The telescope is used in three major areas of research: radio astronomy, atmospheric science, and radar astronomy. Since its inception, the telescope has been upgraded several times over the years allowing scientists to make some remarkable discoveries.
In August 1989, the observatory directly imaged an asteroid for the first time in history: 4769 Castalia, while between 2010 and 2011, American astronomers were able to detect the radio emissions from a T dwarf, which has methane absorption lines in its atmosphere.
Cable anchoring structure for the Northern support tower  Arecibo radio telescope.
Cable anchoring structure for the Northern support tower, Arecibo radio telescope.
Mariordo (Mario Roberto Durán Ortiz)
The observatory's main reflector dish surface is made of 38,778 perforated aluminum panels, each about 3 by 6 feet (1 by 2 m), supported by a mesh of steel cables. The observatory itself has three towers, and each tower has four primary cables that hold up a 900-ton equipment platform suspended above the telescope's massive reflector dish, reports NPR.org.
The observatory was damaged by Hurricane Maria in 2017 and was affected by earthquakes in 2019 and 2020. Two cable breaks, one in August 2020 and a second in November 2020, have threatened the structural integrity of the support structure for the suspended platform and damaged the dish.
In August, a cable slipped out of a socket on Tower 4, carving a 100-foot-long gash into the dish. At the time, engineers believed the structure was stable. However, on November 6, a second cable, also on tower four, snapped. The possibility of an additional cable snapping could mean the platform might not hold and could collapse into the telescope's dish.
Cable configusation supporting the huge receiving dish.
Cable configusation supporting the huge receiving dish.
Image Gallery. Arecibo Observatory.
Inspections of other cables revealed breaks and slippages as well. After going over three separate engineering reports, the NSF, which owns the property, has decided the facility is unstable enough that there is no way to repair the damage that does not put personnel at undue risk, according to Space.com.
"Our goal has been to find a way to preserve the telescope without placing anyone's safety at risk," Sean Jones, assistant director for the Mathematical and Physical Sciences Directorate at the NSF, said in a news conference today.
"However, after receiving and reviewing the engineering assessments, we have found no path forward that would allow us to do so safely. And we know that a delay in decision making leaves the entire facility at risk of an uncontrolled collapse, unnecessarily jeopardizing people and also the additional facilities."
View of the Arecibo radio telescope primary dish and the spherical reflector  Arecibo Observatory  P...
View of the Arecibo radio telescope primary dish and the spherical reflector, Arecibo Observatory, Puerto Rico in June, 2019.
Mariordo (Mario Roberto Durán Ortiz)
"The telescope is currently at serious risk of an unexpected, uncontrolled collapse," Ralph Gaume, director of NSF's Division of Astronomical Sciences, said. "According to engineering assessments, even attempts of stabilization or testing the cables could result in accelerating the catastrophic failure. Engineers cannot tell us the safety margin of the structure, but they have advised NSF that the structure will collapse in the near future on its own."
A huge loss to Puerto Rico and the scientific community
The announcement today of the demise of the radio telescope hit people hard. Puerto Rico takes great pride in Arecibo's rich 57-year history, particularly its role in the search for life beyond our planet, also known as the search for extraterrestrial intelligence (SETI).
The Arecibo message as sent 1974 from the Arecibo Observatory.
The Arecibo message as sent 1974 from the Arecibo Observatory.
Arne Nordmann
In the 1970s, it was used to beam a message about Earth and humanity into space, along with the National Radio Astronomy Observatory at Green Bank, West Virginia through a NASA program called Microwave Observing Program (MOP). MOP was planned as a long-term effort to conduct a general survey of the sky and also carry out targeted searches of 800 specific nearby stars.
Ashley Zauderer, program director at the observatory says the community at Arecibo is the observatory's true treasure. "There's an incredibly diverse and amazing group of scientists and dedicated staff and engineers at the observatory, and I mean, I think it is their passion to continue to explore, to learn, and that is the true heart and soul of Arecibo," she said.
More about Arecibo Telescope, Puerto rico, Radio astronomy, Cables, National Science Foundation
 
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